We have to rely on automated translation tools (our Japanese is not good enough),
these have some issues with converting artist
names and song titles that are not in Latin text. In addition there are
inconsistencies between the names of the same songs from one week to the next.
We have tried to make the names consistent and map them as best we can, but
there are more corrections to be made.

We would be glad to hear from anyone who can tell us where to get validated
charts for Japan from before 1989.

Atributes

The attributes we use from this data are:

artist: The artist

name: The name of each song

position: The peak position the song reached in the weekly chart

date: The month in which the song first entered the chart

weeks: The number of weeks the song was in the chart

artist

There are a wide range of ways to assign scores to artists in order to
work out which artists are most significant. Here is one listing,
of the top five artists of each half decade within this chart.
This has been calculated using a score that combines the position
and the number of weeks in the charts.

If we want to compare artists across the whole duration of this chart
we need to remove the systematic bias that comes from the different chart
dynamics for different eras. We can do that
by first ording all the songs by success within a given year and then using this
order to define a score (for example assigning 1.0 to the number 1 song, 0.5 to
the number 2 and so on).